{ "background": "Community health centres are critical nodes in primary healthcare delivery, yet systematic evaluation of their operational efficiency, particularly service yield, remains methodologically underdeveloped. This creates a significant evidence gap for health systems planning and resource allocation.", "purpose and objectives": "This case study aimed to develop and apply a robust quasi-experimental methodology to measure longitudinal service yield improvement within a network of community health facilities. The primary objective was to isolate the effect of a multi-component health systems strengthening intervention from secular trends.", "methodology": "We employed a difference-in-differences design, analysing longitudinal administrative data from intervention and matched control centres. The core statistical model was $Y{it} = \\beta0 + \\beta1 \\text{Intervention}{i} + \\beta2 \\text{Post}{t} + \\delta (\\text{Intervention}{i} \\times \\text{Post}{t}) + \\epsilon{it}$, where $Y{it}$ is the outpatient attendance per clinical staff month. Inference was based on cluster-robust standard errors to account for facility-level correlation.", "findings": "The intervention was associated with a significant increase in service yield. The adjusted differential effect was an 18.7% rise in outpatient attendance per clinical staff month (95% CI: 12.3% to 25.1%). Qualitative data identified streamlined patient triage and logistics as a key mediating theme for the observed gains.", "conclusion": "The applied quasi-experimental design provided a credible counterfactual, demonstrating a substantial, statistically significant improvement in service yield attributable to the systems intervention. This underscores the value of rigorous impact evaluation in operational health research.", "recommendations": "Health policymakers should integrate quasi-experimental designs into routine health systems monitoring. Future interventions should explicitly target logistical and triage processes, which were identified as critical leverage points for yield improvement.", "key words": "health systems research, quasi-experimental design, difference-in-differences, service yield